Steerable soil displacement hammer

ABSTRACT

The invention relates to a steerable underground rocket for boring horizontally in the earth, having a body which can rotate about a longitudinal body and having a forward-drive head which is mounted such that it can rotate with respect to the body, with relative rotation of the body with respect to the forward-drive head causing the forward-drive head to be pivoted out to an asymmetric constellation, or causing the forward-drive head to be pivoted in to a symmetrical constellation, and having holding means for holding it in the surrounding area, which holding means allow relative rotation of the body and simultaneous pivoting of the forward-drive head, in which case the underground rocket can be operated in the forward the reverse directions, and the holding means are arranged in the area of the pivoting axis of the forward-drive head.

[0001] The invention relates to a steerable underground rocket for forming horizontal bores in the ground having a forward-drive head, which can rotate with respect to the rocket body, and to a method for steering such an underground rocket, and claims priority over German Patent Application 100 52 574.1, to whose contents reference is made.

[0002] Fundamentally, when boring underground, there is a need to guide the underground rocket to a specific destination, or to move it on a desired track. Particularly when boring horizontally, the directional accuracy of the underground rocket, which in some cases is used in particular underground in densely built-up regions with a complex infrastructure, plays a major role. Firstly, the underground rocket must be able to accurately reach a destination trench, which is frequently tightly constrained, in order to carry a pipe or a cable to a desired position, or in order to make it possible to emerge from the earth's surface at a specific point. Secondly, uncontrolled deviation of the underground rocket from the nominal boring axis can lead to damage to underground pipelines or fittings.

[0003] In the last 20 years, numerous underground rockets and methods for such appliances have therefore been developed in the prior art, in order to steer an underground rocket of this type as accurately as possible, or to move it in a straight line as reliably as possible.

[0004] The majority of the underground rockets which have been developed either operate on the principle that the rocket has a forward-drive head which can be moved from a central or symmetrical position to an asymmetric position in order to initiate a turn for the underground rocket (Group I), or they have an asymmetric forward-drive head, with the forward-drive head or the underground rocket being rotated continuously when moving in a straight line, and with the rotation being interrupted at a specific angular position in order to initiate a turn (Group II).

[0005] A Group I appliance, that is to say an appliance with an adjustable forward-drive head, is described, for example, in DE 37 35 018 A1. Appliances such as these have a mechanism in order either to pivot a forwarddrive head (which is symmetrical in the initial position) out of the symmetrical position for example by means of an eccentric ring or in order to move an eccentrically mounted symmetrical forward-drive head by rotation from the boring axis relative to the appliance. In all cases, the mechanism (which can be operated mechanically or hydraulically) leads to the appliance being moved from a symmetrical “straight ahead” basic arrangement to an asymmetric “turning” arrangement. It is necessary to know the relative position of the forward-drive head with respect to the underground rocket in order to control these appliances. This relative position can be transmitted by means of appropriate sensors to an operator, who can then use further measurement and display devices to determine the position of the underground rocket, and to change the movement direction.

[0006] In Group II steerable underground rockets, such as those described, for example, in U.S. Pat. No. 4,907,658, a permanently asymmetric, for example inclined, forward-drive head leads to a continuous steering movement of the underground rocket when it is being driven forward. In order to move straight ahead, the underground rocket or the forward-drive head is caused to rotate, which leads to a tumbling boring movement of the appliance, running essentially straight ahead. In order to maintain the continuous rotation of the head or of the appliance, U.S. Pat. No. 4,694,913 provides a mechanical device which is arranged outside the borehole and uses a linkage to rotate the underground rocket. Although this apparatus and procedure allow the underground rocket to be controlled to a certain extent, they involve considerable design and mechanical complexity since, in addition to the system for driving the underground rocket forward, a system must be provided for rotation, and a linkage must be provided for transmitting the rotation. The linkages are relatively rigid, impede the steering process, and cannot be moved from the trench to the surface. In some appliances such as these, a constricted flexible linkage is used as the first linkage behind the underground rocket in order to allow the underground rocket to carry out any steering movements whatsoever.

[0007] Other underground rockets avoid this complexity for moving in a straight line by using their own systems for rotating the underground rocket or the forward-drive head, as is described, by way of example, in DE 39 11 467 A1.

[0008] In all cases, the advantage of the steerability of an underground rocket leads to not inconsiderable use of materials, costs and operating complexity.

[0009] In addition to horizontal boring methods using underground rockets, boring methods and apparatuses are also known in which a linkage which is provided with a forward-drive head is introduced into the ground via a forward-drive unit which acts outside the borehole, as is described, by way of example, in DE 92 07 047 U1. In this method, the linkage which is required for controlling or rotating the asymmetric forward-drive head is already provided for the forward drive and is used for rotation, so that the problem of rotation when moving underground rockets straight ahead does not arise. However, extensive equipment must be provided for each borehole for this purpose and, in particular, must be transported (linkage, drive), thus increasing the amount of effort and the costs.

[0010] PCT-WO 94/05941, to which reference is hereby made, attempts to solve the problem of steering an underground rocket by means of a Group I appliance, in which the forward-drive head can be moved from a symmetrical position (boring in a straight line) to an asymmetric arrangement (turning) by rotation relative to the underground rocket. In this appliance, the forward-drive head is in the form of a cone with guide plates which extend from the tip of the head along the forward-drive axis, in order to fix the head when driving forward and during steering, and has a longitudinal axis which is inclined to the forward-drive axis of the appliance. The forward-drive head has a rear contact surface, by means of which it makes contact with a front contact surface on the underground rocket, and on which the forward-drive head is rotated. The plane of these contact surfaces is inclined to the appliance longitudinal axis. This makes it possible to rotate the appliance casing about its longitudinal axis, while the earth holds the forwarddrive head firmly by means of the guide plates.

[0011] Such casing rotation allows the forward-drive head to be moved to an eccentric position with respect to the appliance casing, in which position it will turn.

[0012] The rotation angle—referred to as the difference angle in the following text—between the forward-drive head and the appliance casing or the two limit positions of the forward-drive head is governed by a driver pin, which is connected to the forward-drive head and engages in a circular slot in the appliance casing. When the pin is located at one end of the appliance slot, then the forward-drive head is in its position for moving in a straight line (straight-ahead position), while, at the other end of the appliance slot, it is located in the position for turning (steering position).

[0013] In order to move the underground rocket from moving in a straight line onto a specific turning track, the appliance casing can be rotated by means of the compressed-air hose sufficiently for the appliance to achieve the desired angular position (initial position) for the desired turning track.

[0014] This rotational movement may be composed of two phases. In this case, the first phase is for only the appliance casing to be rotated first of all, until the driver pin has moved through the entire difference angle from the straight-ahead position to the steering position. As soon as this has been done, the forward-drive head and the appliance casing are coupled to one another for the rest of the rotational movement, that is to say the appliance casing and the forward-drive head rotate together until the initial position for turning is reached. In the process, considerable forces must be applied, since the deflection of the forward-drive head causes a lateral movement of the surrounding earth and the forward-drive head has to move earth by means of its guide plates during the rotation process. This is exacerbated by the fact that earth has been compressed by the bore face of the forward-drive head.

[0015] It is necessary to determine, above the ground, the angular position, with respect to the appliance longitudinal axis, in which the steering position is located, that is to say that end of the casing slot which governs turning.

[0016] If, for example, the steering position is in the 6 o'clock position when boring in a straight line and it is intended to move the underground rocket from this position to a curved track running upward in a vertical plane, then the steering position is changed to the 12 o'clock position. This is done by using the compressed-air hose to rotate the appliance casing. If the forward-drive head or its driver pin is in the straight-ahead position, then the appliance casing is first of all rotated through the difference angle on its own until the driver pin is located at the other slot end in the steering position, and the casing is then rotated, together with the forward-drive head which is now in the steering position, to the 12 o'clock position.

[0017] Since the steering head position is unknown outside the borehole, it is also impossible to find out there what hose rotation is required—with or without overcoming the difference angle—to move the steering position to the correct initial position for turning.

[0018] Owing to these difficulties, the appliance described above has been developed in DE 199 10 292 A1, to which reference is hereby made, such that, when changing from movement in a straight line to turning, the forward-drive head position at that time with respect to the appliance casing and the position of the driver pin in the casing slot are determined first of all, and the appliance together with the forward-drive head is then set to the desired turning track, or is moved to the initial position for turning, by rotating the compressed-air hose.

[0019] However, the problem still remains that the forward-drive head is fixed in the highly compressed earth surrounding it. It is virtually impossible to use the appliance described in PCT-WO 94/05941 in practice, since the forces required to rotate the underground rocket and the forward-drive head are so large that rotation is frequently impossible or leads to kinking of the compressed-air hose. Furthermore, the guide plates on the forward-drive head often result in uncontrolled deflection of the appliance in an undesirable direction, for example due to stones or the like.

[0020] DE 199 47 645 A1 describes a process in which the underground rocket is rotated manually between two or more positions on a path section basis via the supply line, that is to say discontinuously via the supply line, with the forward-drive head being permanently arranged asymmetrically.

[0021] For turning, the underground rocket is driven forward without any change in its angular position over a specific path section. For moving in a straight line, the path section-by-path section oscillating movement makes it possible to change between the 12 o'clock position and the 6 o'clock position. When moving in a straight line, this leads to an oscillating movement in the vertical axis.

[0022] This method admittedly makes steering easier, since the forward-drive head is no longer rotated relative to the underground rocket and, in consequence, need not have any guide plates. However, when moving straight ahead, it is necessary to carry out a continuous to and fro steering movement by means of the compressed-air hose, which in some circumstances leads to undesirable control effort.

[0023] The invention is now based on the object of providing a method which allows an underground rocket to be moved straight ahead and to be steered easily. The invention is also based on the object of providing an underground rocket which is suitable for this method.

[0024] The object is achieved by a steerable underground rocket according to the independent apparatus claims, and by a method for operating a steerable underground rocket as claimed in the independent method claims.

[0025] Preferred embodiments are the subject matter of the dependent claims.

[0026] The present invention is based on the knowledge that the guide plates which are arranged on the conventional forward-drive head are not required for operation of the steerable underground rocket. This is because, when the underground rocket is being driven forward, the forward-drive head essentially maintains its original steering position setting (path of least resistance) just on the basis of the earth surrounding it. In consequence, when driving forward, no forces are produced in the ground which cause the forward-drive head to be deflected from straight-ahead motion or cause it to be pivoted back from the steering position. In fact, the forces which act on the forward-drive head while boring actually lead to the forward-drive head essentially maintaining its position with respect to the underground rocket.

[0027] In order to change the steering position of the forward-drive head with respect to the underground rocket, it is now in fact necessary to ensure that rotation of the body of the underground rocket via the supply line does not at the same time lead to undesirable rotation of the forward-drive head, so that its longitudinal axis does not change with respect to the appliance longitudinal axis. In the prior art, this function is likewise carried out by the guide plates on the forward-drive head.

[0028] According to the invention, this problem is solved by providing holding means only in the rear region of the forward-drive head, that is to say in the vicinity of the axis about which the forward-drive head pivots.

[0029] In one particularly preferred embodiment, the holding means are in the form of an oversized forward-drive head. This has the advantage that the forward-drive head can be rotated, since only the greater frictional resistance of the holding means in the ground may be overcome, although the holding means also ensure isolated rotation of the body, since a smaller friction resistance may be overcome for rotation of the rocket body than for rotation of the forward-drive head. In this case, the holding effect of the holding means can be increased as required by the choice of its shape, or can be reduced down to the relatively low but adequate holding force provided by an oversized head with a smooth outer surface.

[0030] In order also to avoid the pivoting resistance in the bore face, the underground rocket according to the invention may have a device for reverse operation, and may be moved away from the bore face for steering. The front area of the forward-drive head is then no longer surrounded by compressed earth, but lies freely in the channel in the earth with a full cross section, so that friction forces occur only in the rear area of the forward-drive head during pivoting, and lateral movement of the earth during pivoting of the forward-drive head is considerably reduced, and preferably avoided.

[0031] It is particularly advantageous to use the technique of moving the underground rocket in reverse in conjunction with an oversize head, in order to carry out the steering process. The oversize forward-drive head not only ensures that the body of the underground rocket, which has a smaller diameter, can be rotated easily with the aid of the longitudinal body, (for example the supply line) while in the process ensuring that the head is held adequately in the ground, but also that the head finds an adequate pivoting space when pivoting, when the underground rocket and hence the forward-drive head have been moved backward, in order to remove the forward-drive head from the bore face. However, the oversize section can also be provided separately from the forward-drive head and can then be connected to the forward-drive head via a coupling element.

[0032] In this case, it is advantageous for the forward-drive head not to have any elements which cause displacement of the surrounding earth during pivoting once the underground rocket has been moved back. In one embodiment of the invention, the oversize section can also be provided on an element, for example a ring, which does not change its axial position during pivoting of the forward-drive head, so that there is no need to overcome any friction resistance of the earth during pivoting, either.

[0033] During pivoting of the head, the underground rocket can be moved forward and backward two or more times, in order to further ease the steering process.

[0034] The underground rocket is preferably equipped with a probe and roll sensors, in which case at least one Hall sensor can be used for detection of the steering direction of the forward-drive head.

[0035] The invention will be explained in more detail in the following text with reference to an exemplary embodiment which is illustrated in the drawing, in which:

[0036]FIG. 1 shows an underground rocket according to the invention in the symmetrical straight-ahead position;

[0037]FIG. 2 shows the underground rocket shown in FIG. 1, in an asymmetric turning position;

[0038]FIG. 3 shows the underground rocket shown in FIG. 1, with the forward-drive head located in the bore face;

[0039]FIG. 4 shows the underground rocket shown in FIG. 2, with the forward-drive head located in the bore face;

[0040]FIG. 5 shows the underground rocket shown in FIG. 1 after moving backward, before the steering process;

[0041]FIG. 6 shows the underground rocket shown in FIG. 5, after the steering process.

[0042] The underground rocket 1 has a forward-drive head 2 and a body 4 with a hammer mechanism. The head 2 has a rotation journal 7 and is mounted in the front end of the body via a rotating bearing 8 with clamping pins 9 such that it can rotate. The rotation journal 7 and the rotating bearing 8 are arranged such that the rotation axis V of the forward-drive head 2 is arranged at an angle α with respect to the axis K of the body 4.

[0043] The rotation plane R, which is formed by the rear contact surface 10 of the forward-drive head 2 and by the front contact surface 12 of the body 4, lies at right angles to the rotation axis V of the forward-drive head. This plane, and hence also the rear contact surface 10 of the forward-drive head, is likewise at an angle α with respect to the plane of symmetry or axis A of rotational symmetry of the forward-drive head 2, with this angle α corresponding to the angle between the rotation journal axis and the axis of symmetry A. This means that the axis of symmetry A of the forward-drive head 2 can be made to coincide with the axis K of the body 4. In this position, the underground rocket is set to “move straight ahead”.

[0044] For turning, the forward-drive head 2 is pivoted about an axis at right angles to the plane of the drawing by rotating the body 4 about the axis K, so that the axis of symmetry A of the forward-drive head 2 moves away from the axis K of the body. This can be achieved by means of the compressed-air hose for the hammer mechanism (not shown).

[0045] In order to set the desired boring direction, the forward-drive head 2 may also be rotated together with the body 4 via a stop 18, as soon as it has reached the “turning” (asymmetric) position.

[0046] As is shown in FIGS. 2 and 3, while boring, the forward-drive head 2 is located in the bore face, where the earth is generally compressed and thus fixes the position of the forward-drive head 2 with respect to the body 4, but at the same time making it more difficult or impossible for the forward-drive head axis A to pivot with respect to the body axis K.

[0047] As is shown in FIGS. 5 and 6, the underground rocket can be moved backward away from the bore face by means of a hammer control process in order then to allow the axis A of the forward-drive head to be pivoted without any problems within the earth channel into and out of the steering position.

[0048] The forward-drive head 2, which is in the form of a stepped head, has an oversize section 3 at its rear end, close to the body.

[0049] The oversized section 3 not only ensures that the head can be pivoted without any problems, but also reduces the friction of the body 4 of the underground rocket while at the same time fixing the forward-drive head 2 in terms of rotation in the ground.

[0050] In order to make the steering process even easier, the underground rocket can be moved forward and backward while carrying out the steering process.

[0051] The body has a probe with position Hall sensors 20 in order to determine the orientation of the forward-drive head 2 with respect to the body 4. Buffers 22, 24 protect the probe 20 against the hammer effect of the forward-drive unit of the underground rocket. The body 4 has transmission slots 26 in order to improve the signal transmission from the probe, and has a rotation protection device 28 to ensure the reproducibility of the sensor signal with respect to the rotation angle between the forward-drive head 2 and the body 4. 

1. A steerable underground rocket for boring horizontally in the earth, having a body (4) which can rotate about a longitudinal body and having a forward-drive head (2) which is mounted such that it can rotate with respect to the body, with relative rotation of the body (4) with respect to the forward-drive head (2) causing the forward-drive head (2) to be pivoted out to an asymmetric constellation, or causing the forward-drive head (2) to be pivoted in to a symmetrical constellation, and having holding means (3) for holding it in the surrounding area, which holding means (3) allow relative rotation of the body (4) and simultaneous pivoting of the forward-drive head (2), wherein the holding means (3) are arranged in the area of the pivoting axis of the forward-drive head.
 2. The steerable underground rocket as claimed in claim 1, wherein the underground rocket can be operated in the forward and reverse directions.
 3. The steerable underground rocket as claimed in claim 1 or 2, wherein the holding means are arranged exclusively in the area of the pivoting axis.
 4. The steerable underground rocket as claimed in one of claims 1, 2 or 3, wherein the forward-drive head has an oversize section (3).
 5. The steerable underground rocket as claimed in one of the preceding claims, distinguished by a probe (20).
 6. The steerable underground rocket as claimed in one of the preceding claims, distinguished by at least one roll sensor (20).
 7. The steerable underground rocket as claimed in one of the preceding claims, distinguished by at least one Hall sensor (20) for detection of the position of the forward-drive head (2).
 8. A method for steering a steerable underground rocket which is located in the bore face of a bore and has a forward-drive head (2) which can be rotated between a symmetrical alignment and an asymmetric alignment and has holding means (3), wherein the underground rocket is moved back from the bore face for steering and is rotated about a longitudinal body which is connected to the body of the underground rocket, thus resulting in relative rotation between the body (4) of the underground rocket and the forward-drive head (2).
 9. The method as claimed in claim 8, wherein the underground rocket is moved forward and backward during the rotation process. 